(Sorry for not finishing the title; updated)

cc @kbsriram @agl - if either of you can do a quick triage on if it's user error (in which case, I'll open a PR with docs) or if this is a legit issue.

I tried taking a whack at fixing it, but the signature serialization is a bit .... tightly coupled with writing out a signature packet. It didn't seem clear on the right way to refactor it, so I'm going to have to give up on fixing it.

@paultag @agl Seems like EmbeddedSignatures (0x19: Primary Key Binding Signature from RFC4880 Section 5.2.1) are not currently supported. Taking a look at the code in addSubKey() in openpgp/keys.go:

if sig.SigType != packet.SigTypeSubkeyBinding && sig.SigType != packet.SigTypeSubkeyRevocation {
	return errors.StructuralError("subkey signature with wrong type")
}

Seems like only SigTypeSubkeyBinding (0x18) is supported. I am planning to take a shot at implementing this. Any poc code or notes/docs you could share regarding this would help me get a jumpstart on this issue.

Per the accepted #44226 proposal and due to lack of maintenance, the golang.org/x/crypto/openpgp package is now frozen and deprecated. No new changes will be accepted except for security fixes. The package will not be removed.

If this is a security issue, please email security@golang.org and we will assess it and provide a fix.

If you're looking for alternatives, consider the crypto/ed25519 package for simple signatures, golang.org/x/mod/sumdb/note for inline signatures, or filippo.io/age for encryption. You can read a summary of OpenPGP issues and alternatives here.

If you are required to interoperate with OpenPGP systems and need a maintained package, we suggest considering one of multiple community forks of golang.org/x/crypto/openpgp. We don't endorse any specific one.